1. Field of the Invention
Embodiments of the invention relate to an edge type backlight unit and a method for manufacturing the same.
2. Discussion of the Related Art
A range of application for liquid crystal displays has gradually widened because of its excellent characteristics such as light weight, thin profile, and low power consumption. The liquid crystal displays have been widely used in personal computers such as notebook PCs, office automation equipments, audio/video equipments, interior/outdoor advertising display devices, and the like. The liquid crystal display controls an electric field applied to a liquid crystal layer and modulates light coming from a backlight unit, thereby displaying an image.
The liquid crystal display includes a liquid crystal display panel displaying video data and a backlight unit providing light to the liquid crystal display panel. The liquid crystal display panel and the backlight unit are assembled in a stack to form a liquid crystal module. The liquid crystal module further includes a guide member and a case member for fixing the liquid crystal display panel and the backlight unit, and a driving circuit board of the liquid crystal display panel. A panel gap and a backlight unit cavity exist in the liquid crystal module. The panel gap corresponds to a space between the liquid crystal display panel and the backlight unit, and the backlight unit cavity is formed inside the backlight unit to receive a lamp.
The backlight unit is mainly classified into a direct type backlight unit and an edge type backlight unit. The direct type backlight unit has a structure in which a plurality of light sources are disposed under the liquid crystal display panel.
FIG. 1 is a cross-sectional view of a liquid crystal module including an edge type backlight unit using a thermal interface material (TIM). In the edge type backlight unit shown in FIG. 1, a light source 1 is positioned opposite the side of a light guide plate 4, and a plurality of optical sheets 6 are positioned between a liquid crystal display panel 10 and the light guide plate 4. Further, the light source 1 provides light to one side of the light guide plate 4, and the light guide plate 4 converts a line light source or a point light source into a surface light source. Hence, the light is diffused into the entire surface of the liquid crystal display panel 10.
A light emitting diode (LED) having advantages of high efficiency, high luminance, low power consumption, etc. has been recently spotlighted as the light source of the backlight unit. However, the efficiency and the lifespan of the LED are reduced as a temperature of the LED increases. Thus, various heat dissipation designs have been applied to the LED.
As shown in FIG. 1, a metal printed circuit board (PCB) 2 and a cover bottom 7 are attached to each other using a thermal interface material 3. When a complete surface contact between the metal PCB 2 and the thermal interface material 3 is achieved, heat dissipation characteristic of the backlight unit may increase. However, because a process for applying the thermal interface material 3 is manually performed, the uniformity of the application processing is reduced. Hence, a gap is generated between the metal PCB 2 and the cover bottom 7.
FIG. 2 is a plane view of the metal PCB 2 fastened to the cover bottom 7 using a screw 11. As shown in FIG. 2, when the metal PCB 2 is fastened to the cover bottom 7 using the screw 11, a surface contact between a fastening portion ‘a’ of the screw 11 and a non-fastening portion ‘b’ of the screw 11 is not uniform.
In other words, the surface contact between the metal PCB 2 and the thermal interface material 3 is not uniform in the process for attaching the metal PCB 2 to the cover bottom 7 using the thermal interface material 3. Further, the surface contact between the metal PCB 2 and the cover bottom 7 is not uniform in the process for fastening the metal PCB 2 to the cover bottom 7 using the screw 11. Thus, all of the two methods are not sufficient to efficiently dissipate heat.